Abstract: The deactivated catalyst from the FCC (ecat) process is classified by the NBR10004 as a class I dangerous residue, since it contains heavy metals. These residues are designated to a large list of purposes, among them the co-processing. However, many researches are being performed since the 90's decade, with the usage of ecat in mortars and concrete made out of Portland cement, confirming the pozzolanic potencial of the residue when it proves the increase of mechanical strength in advanced ages, slow hydration and small level of permeability. In associations of concrete and steel bars, the material resistance analysis is related to the quality of the concrete portion that protects the steel from deterioration processes, such as corrosion. This research added the ecat to the mortars applied in steel bars aiming to evaluate the behavior of the electrochemical noise technic in the understanding of the protection mechanisms against the corrosion. This technic consists in the registration of current and potential fluctuation generated spontaneously by the electrochemical corrosion reactions. In order to analyze this process, it was produced test pieces made out of Portland cement and sand with different percentages of ecat. After that, steel bars were added to the previously prepared test pieces, forming a typical reinforced concrete structure. The test pieces were emerged in a 3,5% NaCl solution for 4 (four) months. During this period, data of the electrochemical noise was collected weekly in order to prove the spontaneous evolution of the corrosive process. It was generated 36 (third six) curves with the corrosive process monitoring. This technic allowed to track the changes in the events of the general corrosion such as the localized corrosion. In the end of this procedure, it was performed an SEM analysis on the test pieces. It was seen that the chloride ions concentration was bigger in the interface between mortars and steel rather than the test piece external surface. Hence, it was proved that this technic can be used to monitor the corrosion in the structures made out of concrete that are subjected to the process of chloride deterioration, allowing to track the changes in both localized and general corrosion. Keyword: cement portland, ecat, eletrochemical noise